It is common commercial practice to include amylases in detergent compositions to enhance cleaning performance.
Indeed, amylase enzymes have long been recognised in dishwashing, hard surface cleaning and laundry compositions to provide the removal of starchy food residues or starchy films from dishware, flatware, glasses and hard surfaces or to provide cleaning performance on starchy soils as well as other soils typically encountered in laundry applications.
WO/94/02597, Novo Nordisk A/S published Feb. 03, 1994, describes cleaning compositions which incorporate mutant amylases. See also WO/94/18314, Genencor, published Aug. 18, 1994 and WO/95/10603, Novo Nordisk A/S, published Apr. 20, 1995. Other amylases known for use in cleaning compositions include both .alpha.- and .beta.-amylases. .alpha.-Amylases are known in the art and include those disclosed in U.S. Pat. No. 5,003,257; EP 252,666; WO/91/00353; FR 2,676,456; EP 285,123; EP 525,610; EP 368,341; and British Patent specification no. 1,296,839 (Novo). Examples of commercial .alpha.-amylases products are Termamyl.RTM., Ban.RTM. and Fungamyl.RTM., all available from Novo Nordisk A/S Denmark.
It is equally well recognised that amylase deactivation occurs in detergent formulations. The loss of activity of the amylase is among others depending on the presence of adjunct detergent ingredients. One type of adjunct detergent ingredients is the surfactants.
A wide variety of detersive surfactants are known in the literature and in commercial practice. They perform a dual function within the detergent matrix. First, surfactant molecules reduce the interfacial tension between the soil and aqueous phase and thereby gradually remove the stain from the surface by a roll-up, emulsification or solubilisation mechanism. Anionic surfactants are particularly suitable for this function. Secondly, surfactant molecules keep the soil in suspension and prevent redeposition onto the surface. Ethoxylated nonionic and anionic surfactants traditionally serve that purpose.
Therefore, while amylase is known to act on starch stains, there remains a substantial technical challenge in formulating detergent compositions comprising amylase and surfactants in such a manner to meet the consumer's need for superior cleaning performance on soils and in particular, starchy soils.
It is therefore an object of the present invention to provide detergent compositions including laundry, dishwashing and hard surface cleaner, containing oxidative stability-enhanced amylases and surfactants in order to meet the above need.
It is a further objective to formulate laundry detergent compositions which provide effective and efficient surface cleaning of textile, particularly on dingy stains.
It has now surprisingly been found that optimised applications of oxidative stability-enhanced amylase enzymes into detergent compositions is obtained when they are combined with a surfactant system with a specific anionic to nonionic surfactants ratio. In particular, it has been found that these oxidative stability-enhanced amylases in combination with an anionic to nonionic surfactants ratio between 1:1 and 5:1, preferably between 1:1 and 3:1 provide synergistic benefits in the removal of both traditional and specific amylase sensitive stains.
This finding allows either improved performance or a reduction of the surfactant/amylase levels while keeping the same detergency performance.